Diathermy Flashcards
What is diathermy?
The application of high frequency electromagnetic energy used to generate heat in body tissues
How does diathermy produce heat?
Tissues resist the passage of energy and produce heat
Describe electrical fields
- They point away from positive charges and towards negative
- They never cross each other
- Always intersect conductors at right angles
- Stronger fields have closer lines
Shortwave Diathermy uses a frequency of __ to __ MHz
10 - 100
Shortwave Diathermy uses a wavelength of __ to __ meters
3 - 30 meters
Microwave Diathermy uses a frequency of __ MHz to __ GHz
300 MHz to 300 GHz
Microwave Diathermy uses a wavelength of __ mm to __ meters
1 mm to 1 meter
Are shortwaves and microwaves ionizing or non-ionizing? What does this mean?
non-ionizing which means they cannot make molecular bonds or produce ions
What typically is the intensity of the electromagnetic device?
80 - 120 Watts
How can you determine how much energy is absorbed?
The amount of heating cannot be accurately prescribed or directly measured. Therefore you must rely on the patient’s report
What are the thermal effects of diathermy?
Continuous diathermy heats superficial and deep tissues
Describe the 4 dosage effects
Dose I: Lowest level; no sensation of heat
Dose II: Low; Mild heating sensation.
Dose III: Medium; Moderate (pleasant) heating sensation
Dose IV: Heavy; Vigorous heating that is tolerable below the pain threshold
Heating tissue 1 degree helps to do what?
reduce mild inflammation
Heating tissue 2-3 degrees helps to do what?
Decrease Pain and Muscle Spasm
Heating tissue 3-4 degrees helps to do what?
Increase Tissue Extensibility
What are the non-thermal effects of diathermy?
Low level pulsed diathermy causes changes at the cellular level, making the cell wall more permeable
What are the 2 types of diathermy delivery?
Capacitance and Inductance
What type of field does capacitance diathermy use?
Electric
What type of electrodes does capacitance diathermy use?
air space plates or pad electrodes
What type of circuit is used during capacitance diathermy?
series, therefore the patient is part of the circuit
What tissues are heated with the use of capacitance diathermy?
Ones high in electrolytes, such as muscle, blood, etc.
How deep does capacitance diathermy heat?
1 cm
What type of field does inductance diathermy use?
magnetic
What type of electrodes does inductance diathermy use?
drum or cable
What type of circuit is used during inductance diathermy?
Parallel, therefore the patient is not part of the circuit
What tissues are heated with the use of inductance diathermy?
Subcutaneous Fat
If there is little subcutaneous fat in the area, how deep does inductance diathermy heat?
3 - 4 cm
Which tissue has the most resistance to the passage of an electric field?
Fat
How many currents are produced with inductance diathermy?
2: initial current is created within the electrode and the secondary current is produced is called eddy currents
Microwave diathermy uses a ___ frequency and ____ wavelength than shortwave diathermy
higher
shorter
When should you use microwave diathermy?
if subcutaneous fat is <0.5 cm thick
Which tissue absorbs the most microwave diathermy?
bone
What are the indications for the use of diathermy?
- Control of edema
- Pain control
- Wound healing
- Neuropathy
- Bone healing
- Osteoarthritis symptoms
- Ischemic skin flaps
- Cerebral diseases
What are the advantages of diathermy over other thermal agents?
- Can heat larger areas than ultrasound
- SWD is not reflected by bone therefore there is no risk of periosteal burning
- Little time for application and set-up
What are the disadvantages of diathermy over other thermal agents?
- Equipment is not always available
- MWD is reflected at tissue interfaces therefore the formation of standing waves, can form hot spots
What is the Absolute Contraindication to diathermy?
pregnancy
5 other contraindications to diathermy
- Metal implants
- Malignancy
- Over the eyes
- Over the testes
- Over growing epiphyses
- Internal organs
- Pacemakers
- Electronic devices
- Metal implants
Precautions for Diathermy
- Near electronic or magnetic equipment
- Obesity
- Copper-bearing intrauterine contraceptive devices
- Skeletal immaturity
Why use diathermy over US?
It can heat larger areas than ultrasound and there is a longer window for stretching
